Hyperthyroidism in pregnancy

Pregnancy	Drugs of choice
First trimester	Propylthiouracil (PTU) - risk of using MMI (higher risk of birth defects) out-weighs the low risk of developing hepatotoxicity with PTU during this time period
Second & third trimesters	Methimazole (MMI) - Used for remainder of pregnancy - to reduce the risk of PTU-induced hepatitis Carbimazole (CBZ) - converted into methimazole in the body - 1mg of carbimazole is approximately equivalent to 10 mg of propylthiouracil. *can also continue on PTU, given hepatic function monitored every 4 weeks with thyroid function tests. (no prospective data show monitoring of liver function tests will be helpful in preventing hepatotoxicity)

** the antithyroid drug dose should probably be tapered if (thyroid stimulating hormone) TSH rises into the normal range

References

1. http://www.uptodate.com/contents/antithyroid-drugs-beyond-the-basics

2. http://www.fda.gov/Safety/MedWatch/SafetyInformation/ucm209256.htm

3. http://friedmanfellows.com/assets/pdfs/elibrary/2014/PTU-paper.pdf

4. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3821452/

5. https://clinicaltrials.gov/ct2/show/NCT01436994

6. press.endocrine.org/doi/full/10.1210/jcem.86.6.7573